The present invention relates to a hydraulically operated transmission primarily for use in an automobile.
The present applicant has previously proposed a hydraulically operated vehicular transmission shown in Japanese Unexamined Patent Application Publication No. 124469/88, which comprises first- to fourth-speed gear trains G1, G2, G3 and G4 established by corresponding hydraulic clutches C1, C2, C3 and C4, a one-way clutch a incorporated in the first speed gear train G1 for permitting overrotation of an output side, and a first-speed maintaining clutch CH also incorporated in the first-speed gear train G1 in parallel with the one-way clutch a, as shown in FIG. 2.
In this transmission, an input shaft d and an output shaft e are carried in parallel within a transmission case b. The input shaft d is connected to a fluid torque converter g connected to a crank shaft f of an engine, through that end wall i of the transmission case b which is closer to the engine and to which a valve block h is assembled. The first- to fourth-speed gear trains G1, G2, G3 and G4 are interposed in parallel between the input shaft d and the output shaft e. The first-speed hydraulic clutch C1 for establishing the first-speed gear train G1 is disposed at that end of the input shaft d which is opposite to the engine, and the third-speed hydraulic clutch C3 for establishing the third-speed gear train G3 is disposed at that end of the output shaft e which is closer to the engine. The second-speed hydraulic clutch C2 for establishing the second-speed gear train G2 and the fourth-speed hydraulic clutch C4 for establishing the fourth-speed gear train G4 are disposed in a back-to-back relation at an intermediate portion of the input shaft d. Further, a bypass shaft k is connected, through a gear j, to a drive gear G1a of the first-speed gear train G1 connected to the first-speed hydraulic clutch C1, and a first-speed maintaining hydraulic clutch CH is disposed on the bypass shaft k so as to connect the bypass shaft k with the output shaft e through a drive gear and a driven gear of the fourth-speed gear train G4. Thus, when both of the first-speed hydraulic clutch C1 and the first-speed maintaining hydraulic clutch CH have been brought into engagement, the first-speed gear train G1 is established by a path G1' bypassing the one-way clutch a.
In FIG. 2, the reference character GR is a reverse gear train which commonly uses the fourth-speed hydraulic clutch C4 with the fourth-speed gear train G4, so that the reverse gear train GR and the fourth-speed gear train G4 are selectively established, through a selector gear 1, on the output shaft e.
The above described transmission is accompanied by the following problem: Because the three hydraulic clutches C1, C2 and C4 for the first-, second- and fourth-speed gear trains G1, G2 and C4 are disposed on the input shaft d, the input shaft d is too long, resulting in a longer axial size of the transmission.
The present invention has been accomplished with respect to such problem, and it is an object of the present invention to provide a compact transmission having a reduced axial size.